Antigen recognition in the immune system relies on four molecule classes—pattern recognition receptors, MHC molecules, T cell receptors, and B cell receptors/antibodies—distinguished by their polymorphism and mechanism of diversity generation. B lymphocyte development proceeds through defined stages (stem cell, pro-B, pre-B, immature, mature) in the bone marrow, driven by sequential, ordered somatic recombination of immunoglobulin heavy- and light-chain gene segments (V, D, and J for heavy chains; V and J for light chains) mediated by the RAG1/RAG2 recombinase acting on recombination signal sequences. This V(D)J recombination process—governed by combinatorial gene segment selection, allelic exclusion, and negative selection against self-antigen—generates the vast diversity of antigen receptors that underlies adaptive immunity, a central mechanism in immunology.
Antigen recognition in the immune system relies on four molecule classes—pattern recognition receptors, MHC molecules, T cell receptors, and B cell receptors/antibodies—distinguished by their polymor…